"Through a microscope, you can see that the pencil lines are physically on top of the paint and have been applied after the painting was finished," Thierry Ford, the paintings conservator at the National Museum of Norway, explained.
But, while that much has been easy to see, little else is. Pencil-on-paint is not easy to interpret, Ford said, so experts at the museum put some technology to work to better read it.
"We chose to photograph it with an infrared camera to get a clearer picture of the inscription," Ford said. "In an infrared photo, the carbon from the pencil stands out more clearly and makes handwriting analysis easier. And you don't have to impact the painting itself."